/*
 * libipq.c
 *
 * IPQ userspace library.
 *
 * Please note that this library is still developmental, and there may
 * be some API changes.
 *
 * Author: James Morris <jmorris@intercode.com.au>
 *
 * 07-11-2001 Modified by Fernando Anton to add support for IPv6.
 *
 * Copyright (c) 2000-2001 Netfilter Core Team
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>

#include "acconfig.h"

#ifdef HAVE_LIBIPQ_PATH1
#include <libipq.h>
#else
#include <libipq/libipq.h>
#endif

/****************************************************************************
 *
 * Private interface
 *
 ****************************************************************************/

enum
{
  IPQ_ERR_NONE = 0,
  IPQ_ERR_IMPL,
  IPQ_ERR_HANDLE,
  IPQ_ERR_SOCKET,
  IPQ_ERR_BIND,
  IPQ_ERR_BUFFER,
  IPQ_ERR_RECV,
  IPQ_ERR_NLEOF,
  IPQ_ERR_ADDRLEN,
  IPQ_ERR_STRUNC,
  IPQ_ERR_RTRUNC,
  IPQ_ERR_NLRECV,
  IPQ_ERR_SEND,
  IPQ_ERR_SUPP,
  IPQ_ERR_RECVBUF,
  IPQ_ERR_TIMEOUT,
  IPQ_ERR_PROTOCOL
};
#define IPQ_MAXERR IPQ_ERR_PROTOCOL

struct ipq_errmap_t
{
  int errcode;
  char *message;
} ipq_errmap[] = {
  { IPQ_ERR_NONE, "Unknown error"},
  { IPQ_ERR_IMPL, "Implementation error"},
  { IPQ_ERR_HANDLE, "Unable to create netlink handle"},
  { IPQ_ERR_SOCKET, "Unable to create netlink socket"},
  { IPQ_ERR_BIND, "Unable to bind netlink socket"},
  { IPQ_ERR_BUFFER, "Unable to allocate buffer"},
  { IPQ_ERR_RECV, "Failed to receive netlink message"},
  { IPQ_ERR_NLEOF, "Received EOF on netlink socket"},
  { IPQ_ERR_ADDRLEN, "Invalid peer address length"},
  { IPQ_ERR_STRUNC, "Sent message truncated"},
  { IPQ_ERR_RTRUNC, "Received message truncated"},
  { IPQ_ERR_NLRECV, "Received error from netlink"},
  { IPQ_ERR_SEND, "Failed to send netlink message"},
  { IPQ_ERR_SUPP, "Operation not supported"},
  { IPQ_ERR_RECVBUF, "Receive buffer size invalid"},
  { IPQ_ERR_TIMEOUT, "Timeout"},
  { IPQ_ERR_PROTOCOL, "Invalid protocol specified"}
};

static int ipq_errno = IPQ_ERR_NONE;

static ssize_t ipq_netlink_sendto(const struct ipq_handle *h,
                                  const void *msg, size_t len);

static ssize_t ipq_netlink_recvfrom(const struct ipq_handle *h,
                                    unsigned char *buf, size_t len,
                                    int timeout);

static ssize_t ipq_netlink_sendmsg(const struct ipq_handle *h,
                                   const struct msghdr *msg,
                                   unsigned int flags);

static char *ipq_strerror(int errcode);

static ssize_t ipq_netlink_sendto(const struct ipq_handle *h,
                                  const void *msg, size_t len)
{
  int status = sendto(h->fd, msg, len, 0,
                      (struct sockaddr *)&h->peer, sizeof(h->peer));
  if (status < 0)
    ipq_errno = IPQ_ERR_SEND;
  return status;
}

static ssize_t ipq_netlink_sendmsg(const struct ipq_handle *h,
                                   const struct msghdr *msg,
                                   unsigned int flags)
{
  int status = sendmsg(h->fd, msg, flags);
  if (status < 0)
    ipq_errno = IPQ_ERR_SEND;
  return status;
}

static ssize_t ipq_netlink_recvfrom(const struct ipq_handle *h,
                                    unsigned char *buf, size_t len,
                                    int timeout)
{
  int addrlen, status;
  struct nlmsghdr *nlh;

  if (len < sizeof(struct nlmsgerr))
  {
    ipq_errno = IPQ_ERR_RECVBUF;
    return -1;
  }
  addrlen = sizeof(h->peer);

  if (timeout != 0)
  {
    int ret;
    struct timeval tv;
    fd_set read_fds;

    if (timeout < 0)
    {
      /* non-block non-timeout */
      tv.tv_sec = 0;
      tv.tv_usec = 0;
    }
    else
    {
      tv.tv_sec = timeout / 1000000;
      tv.tv_usec = timeout % 1000000;
    }

    FD_ZERO(&read_fds);
    FD_SET(h->fd, &read_fds);
    ret = select(h->fd+1, &read_fds, NULL, NULL, &tv);
    if (ret < 0)
    {
      if (errno == EINTR)
      {
        return 0;
      }
      else
      {
        ipq_errno = IPQ_ERR_RECV;
        return -1;
      }
    }
    if (!FD_ISSET(h->fd, &read_fds))
    {
      ipq_errno = IPQ_ERR_TIMEOUT;
      return 0;
    }
  }
  status = recvfrom(h->fd, buf, len, 0,
                    (struct sockaddr *)&h->peer, (socklen_t *)&addrlen);
  if (status < 0)
  {
    ipq_errno = IPQ_ERR_RECV;
    return status;
  }
  if (addrlen != sizeof(h->peer))
  {
    ipq_errno = IPQ_ERR_RECV;
    return -1;
  }
  if (h->peer.nl_pid != 0)
  {
    ipq_errno = IPQ_ERR_RECV;
    return -1;
  }
  if (status == 0)
  {
    ipq_errno = IPQ_ERR_NLEOF;
    return -1;
  }
  nlh = (struct nlmsghdr *)buf;
  if (nlh->nlmsg_flags & MSG_TRUNC || nlh->nlmsg_len > status)
  {
    ipq_errno = IPQ_ERR_RTRUNC;
    return -1;
  }
  return status;
}

static char *ipq_strerror(int errcode)
{
  if (errcode < 0 || errcode > IPQ_MAXERR)
    errcode = IPQ_ERR_IMPL;
  return ipq_errmap[errcode].message;
}

/****************************************************************************
 *
 * Public interface
 *
 ****************************************************************************/

/*
 * Create and initialise an ipq handle.
 */
struct ipq_handle *ipq_create_handle(u_int32_t flags, u_int32_t protocol)
{
  int status;
  struct ipq_handle *h;

  h = (struct ipq_handle *)malloc(sizeof(struct ipq_handle));
  if (h == NULL)
  {
    ipq_errno = IPQ_ERR_HANDLE;
    return NULL;
  }

  memset(h, 0, sizeof(struct ipq_handle));

  if (protocol == PF_INET)
    h->fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_FIREWALL);
  else if (protocol == PF_INET6)
    h->fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_IP6_FW);
  else
  {
    ipq_errno = IPQ_ERR_PROTOCOL;
    free(h);
    return NULL;
  }

  if (h->fd == -1)
  {
    ipq_errno = IPQ_ERR_SOCKET;
    close(h->fd);
    free(h);
    return NULL;
  }
  memset(&h->local, 0, sizeof(struct sockaddr_nl));
  h->local.nl_family = AF_NETLINK;
  h->local.nl_pid = getpid();
  h->local.nl_groups = 0;
  status = bind(h->fd, (struct sockaddr *)&h->local, sizeof(h->local));
  if (status == -1)
  {
    ipq_errno = IPQ_ERR_BIND;
    close(h->fd);
    free(h);
    return NULL;
  }
  memset(&h->peer, 0, sizeof(struct sockaddr_nl));
  h->peer.nl_family = AF_NETLINK;
  h->peer.nl_pid = 0;
  h->peer.nl_groups = 0;
  return h;
}

/*
 * No error condition is checked here at this stage, but it may happen
 * if/when reliable messaging is implemented.
 */
int ipq_destroy_handle(struct ipq_handle *h)
{
  if (h)
  {
    close(h->fd);
    free(h);
  }
  return 0;
}

int ipq_set_mode(const struct ipq_handle *h,
                 u_int8_t mode, size_t range)
{
  struct
  {
    struct nlmsghdr nlh;
    ipq_peer_msg_t pm;
  } req;

  memset(&req, 0, sizeof(req));
  req.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(req));
  req.nlh.nlmsg_flags = NLM_F_REQUEST;
  req.nlh.nlmsg_type = IPQM_MODE;
  req.nlh.nlmsg_pid = h->local.nl_pid;
  req.pm.msg.mode.value = mode;
  req.pm.msg.mode.range = range;
  return ipq_netlink_sendto(h, (void *)&req, req.nlh.nlmsg_len);
}

/*
 * timeout is in microseconds (1 second is 1000000 (1 million) microseconds)
 *
 */
ssize_t ipq_read(const struct ipq_handle *h,
                 unsigned char *buf, size_t len, int timeout)
{
  return ipq_netlink_recvfrom(h, buf, len, timeout);
}

int ipq_message_type(const unsigned char *buf)
{
  return((struct nlmsghdr*)buf)->nlmsg_type;
}

int ipq_get_msgerr(const unsigned char *buf)
{
  struct nlmsghdr *h = (struct nlmsghdr *)buf;
  struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);
  return -err->error;
}

ipq_packet_msg_t *ipq_get_packet(const unsigned char *buf)
{
  return NLMSG_DATA((struct nlmsghdr *)(buf));
}

int ipq_set_verdict(const struct ipq_handle *h,
                    ipq_id_t id,
                    unsigned int verdict,
                    size_t data_len,
                    unsigned char *buf)
{
  unsigned char nvecs;
  size_t tlen;
  struct nlmsghdr nlh;
  ipq_peer_msg_t pm;
  struct iovec iov[3];
  struct msghdr msg;

  memset(&nlh, 0, sizeof(nlh));
  nlh.nlmsg_flags = NLM_F_REQUEST;
  nlh.nlmsg_type = IPQM_VERDICT;
  nlh.nlmsg_pid = h->local.nl_pid;
  memset(&pm, 0, sizeof(pm));
  pm.msg.verdict.value = verdict;
  pm.msg.verdict.id = id;
  pm.msg.verdict.data_len = data_len;
  iov[0].iov_base = &nlh;
  iov[0].iov_len = sizeof(nlh);
  iov[1].iov_base = &pm;
  iov[1].iov_len = sizeof(pm);
  tlen = sizeof(nlh) + sizeof(pm);
  nvecs = 2;
  if (data_len && buf)
  {
    iov[2].iov_base = buf;
    iov[2].iov_len = data_len;
    tlen += data_len;
    nvecs++;
  }
  msg.msg_name = (void *)&h->peer;
  msg.msg_namelen = sizeof(h->peer);
  msg.msg_iov = iov;
  msg.msg_iovlen = nvecs;
  msg.msg_control = NULL;
  msg.msg_controllen = 0;
  msg.msg_flags = 0;
  nlh.nlmsg_len = tlen;
  return ipq_netlink_sendmsg(h, &msg, 0);
}

/* Not implemented yet */
int ipq_ctl(const struct ipq_handle *h, int request, ...)
{
  return 1;
}

char *ipq_errstr(void)
{
  return ipq_strerror(ipq_errno);
}

void ipq_perror(const char *s)
{
  if (s)
    fputs(s, stderr);
  else
    fputs("ERROR", stderr);
  if (ipq_errno)
    fprintf(stderr, ": %s", ipq_errstr());
  if (errno)
    fprintf(stderr, ": %s", strerror(errno));
  fputc('\n', stderr);
}
